Stoker for solid fuel



, G. M; PELTZ V STOKER For; SOLID' FUEL Filed July 11, 1951 s Sheets-Sheet .1 v j ATTORNEYS,

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H G. M. PELTE-Z s rgm m SOLID sum.

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V a sw m-sum 2 Aug. 23, 1938.

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Aug. 23, 1938. G. M. PELTZ STOKER FOR SEQLID FUEL Filed July l l 1931 3 Sheets-Sheet 3 T 0R. 0, g A TTORNEYS.

memes A... 23,19 3 2,127,933

UNITED STATES PATENT OFFICE 2,127,933 l STOKER r01: some FUEL Gordon M. Peltz, Elmhurst, N. Y., assignor, by mesne assignments, to Henry M. Brooks, New York, N. Y., William Tudor Gardiner, Augusta, Maine, and Jacob H. Nissley, Manheim, Pa., as trustees Application July. 11, 1931, Serial No. 550,127 23 Claims. (Ol.'110-45) My invention relates particularly (although not and an electric motor 8 for driving the moving necessarily exclusively) to those stokers for solid parts of the stoker, together with intermediate fuel, usually coal, which are commonly used for driving mechanism as indicated generally at the the heating of homes, apartment houses, schools, right-hand ends of Figs. 1 and 2. This inter- 5 etc. and hence which must needs operate submediate driving mechanism, and also various stantially completely automatically and with other details of construction of the stoker illuslittle or no attention, trated but not specifically mentioned herein, It is directed especially to improving underfeed rm Pa t O e present nv ntion and other stokers burning graded coal, e. g., coal a conforms can be substituted for them, as will be siderable part of which-is greatly larger than dust understood; they need not be described thereor pulverized, and to providing an improved fore. stoker of the class, indicated. The manner in The burner member I consists generally of a which. this is accomplished, and also various grate l4, perforated for the passage of the air subsidiary accomplishments of the invention, required to burn the fuel, and a base l therefor appear in the description hereinafter of a parproviding a passage for directing the combustioularv embodiment of my invention and the tion air from air conduit 3 to the grate. The grate illustrated, as is common in stokers of this claims which follow.

My invention is not limited to stokers for heatkind, is of the annular or underfeed type, and as is commonin stokers of this kind burning the ing homes, apartment houses and schools howharder coals, is of the upwardly and outwardly 90 ever, asiwill be' understood.

flaring center-underfeed type. It will be under- My copending application Serial No. 606,838, filed April 22, 1932, isa division of the present stood however that where hereinafter I use, for brevity, the term annular grate, there is no application and claims certainmatter formerly described and illustrated in this present app1ilimitation to grates that are circular in plan view cation. like the grate l4, except as the contrary inter- In the accompanying drawings, in which an pretation may be necessary.

embodiment of 'my invention particularly suited It will be understood from the drawings of for the harder coals is illustrated: Fig. 1 is an course that the fuel conveyor 66 forces the fuel elevational view of astoker embodying my inven- (coal) upwardly through'the elbow 32 and thence tion, partly in section. Fig. 2 is a plan view of over the grate, and that the ashes are discharged the same, partly in section at various levels as over the outer edge of the latter. Usually they are permitted to fall as they will from the edge will be understood from the description which follows. Fig. 3 is a vertical section through the of the grate. The ash pit to which the ashes fall is the space outside the air-chamber casing l5.

grate and adjacent mechanism, drawn to a larger scale than. that of Fig. 1. Fig. 4 is a detail of To get the ashes falling from the outer edge of the grate to the ash screw 58 which serves to the construction at the under side of the ash paddle carrier. Fig. 5 is a plan view of one of take them out of the furnace (especially where, the rings of which the grate is preferably built as here, they are allowed to fall off the grate up. Fig. 6 is a vertical section through one 01' throughout the whole of the circumference of these rings. Fig.7 is a vertical section through a the latter), I preferably employ as a part of the ash conveyor, one or more ash paddles 49, or

pair of these rings, showing the assembled relasorapers as they are sometimes called. Ash

tion. Fig. 8 is an elevation at the inner end of t e ash C yor. paddles, stirrers or scrapers of this general type In general. t e o e here illustrated, quite like are already known. These revolve slowly within the ash, pit and around the vertical center line 5 stokers of the same class heretofore known, consists of a burner member I which is placed within of the grate l4 andgradually work fallen ashes the furnace (the inner walls of the furnace being around to the intake port for the ash conduit 5; shown at 2 for illustrative purposes), a ir conthe latter is conveniently provided in the fitting duit 3 for carrying the combust on t0 e b l 21 by means of which one end of the ash con- 1161, a fuel conduit 4 through which the fuel is duit 5 may be supported on the burner memher I; by preference these paddles 49 are resupplied to the grate by means of the screw conveyor 66, an ash conduit 5 through which the volved in a substantially horizontal path, and by ashes are taken away from the furnace by means preference in a path above the conduits before mentioned; this last feature prevents ashes acof screw conveyor 58, a fuel hopper 6, a blower or rotary fan 1 for supplying the combustion air, cumulating on the conduits until the pile or piles -III ' over the grate.

thereon reach to the upper edge of the grate and then prevent uniform flow of the coal and ashes It is not necessary to provide a plate or other surface immediately below thepath of these paddles to catch the ashes as they fall from the grate edge, although such a plate can be used of course; the ashes can be allowed to collect in the bottom of the furnace outside the grate base l until they reach the height of the paddle path; the paddles will prevent the ashes accumulating above 'point of course. To support these paddles and to conveniently provide for the supporting of the grate and the feeding of the air to thegrate (or, in general, to provide a satisfactory and convenient construction for a complete burner member I) 1 preferably provide the grate base IS with an upwardly rising internal wall 5|, which may be provided by the inner end of the coal conduit 4 which is fastened to the grate base l5 as before described, and on this I rest the grate l4 as appears from the drawings and as'will later be referred to again; then, externally of this internal wall I provide the base member l5 with an upwardly rising wall 52 providing, or enclosing between it and the grate, the necessary passage for leading combustion air from the air conduit 3 to the grate, and on this wall I provide a substantially annular substantially horizontal bearing 53 on which I mount a ring 54 carrying the ash paddle or paddles 49. Usually I interpose a ball bearing between the wall 52 and ring 54 as illustrated. In order to keep the ashes and dust from this bearing at 53, I usually make the diameter of this bearing materially less than the outside diameter of the grate l4 itself (see Figs. 1 and 3) so that the ashes fall well outside this bearing; and also I usually overhang the bearingwith an extension 55 of the external wall 52, to act as a shield for the bear ing, and I also let the ring 54 depend from the bearing or provide it with a skirt as at 56; the under side of this skirt may be provided if necessary with paddles 51 so inclined that they push ashes coming against them outwardly away from the. bearing at 53 as the ring 54 is rotated. Inasmuch as the paddles 49 will seldom if ever be used except when an ash conveyor is used on the machine, as well as for other reasons, it is convenient to provide for the driving of this ring from the ash conveyor. Thus in the present instance the screw conveyor 58 for the ashes carries at its inner end a bevelled gear 59 (see Fig. 2) which drives a vertical shaft tit carrying a spur gear 6| meshing with internal teeth on the skirt 56. The whole ash system may therefore constitute a unit as it were, and either used as a whole or omitted as a whole.

To help break up such large ash and cinders as otherwise may be too large to pass readily through the space between the furnace wall and the edge of the grate, a member 62 may be mounted on a rotating supporting structure placed well below the top of the grate (where there is more room for the rotating structure), this member extending thence upwardly into the space between the outer edge or the grate and the furnace wall. This member 62 may be a simple plate or bar. Where an ash paddle or paddles 49 are employed, the bar or other member 62 (or all of them if there be more than one) can usually be readily mounted on one or more of these paddles or on the carrier of the paddles; for example, these ash paddles may be hollowed out horizontally as indicated in Fig. 3, and a turned over end of a bar 62, bolted in this recess of one of them as there shown.

As is frequently the case with grates of the type illustrated, the grate structure has a downwardly projecting encircling ring 91 at its outer edge (Fig. 3) Due to the different temperatures experienced, simultaneously by the grate itself and by such a ring, and the consequent difference between the expansions and contractions of the grate and the expansions and contractions of the ring, the satisfactory attachment of such a ring to the grate edge is frequently not attained. To

overcome this difliculty, I make the ring 91 separate from the grate, and attach the two by a bolt or bolts 98 which I place in a non-shearable relation to the grate. and the encircling member 91; specifically, I leave a mid-portion of each bolt free of contact with the grate and member, for example, as appears in Fig. 3; and to the latter end I preferably space each bolt inwardly from the point 99 of engagement of the grate' with the downwardly projecting encircling member, i. e., I place it within the air chamber which is immediately outside the grate and from which the air for combustion passes into the grate, as will also be apparent from Fig. 3. With such a construction and with such a disposition of the bolts I find that there is little or no tendency for the bolts or the ring to be broken by the unequal expansions and contractions of the grate and the encircling member. In order to make a permanently airtight joint at the point'of engagement 99 between the grate and encircling member, I usually place a fireproof gasket Hill (such as asbestos) between the two, giving this such a shape (for example, circular in cross-section) that it contacts with the two at only relatively small portions of their opposing faces (Fig. 3). Quite probably the compressibility of such gaskets helps to maintain the integrity'of the bolts 98. To complete the enclosure of the air chamber or passage immediately surrounding the grate, that is to say, to form the joint between the encircling member 91 and the upwardly rising wall 52 of the grate base I5, I provide the wall 52 with an upwardly opening encircling trough IDI into which the lower edge or the encircling member 91 extends, and this trough I more or less fill with a fluent material I02, usually a solid material in granular form, and ordinarily common sand. This forms an air seal at this point, the permanent efliciency of which is entirely unaffected by temperature changes and consequent expansions and contractions of 91 and 52. By supporting the grate l4 at its inner periphery (that is to say, for example, on the wall 5! as before described), no metal to metal contact or weightsupporting connection is necessary at the opposite side of the air chamber, namely, between the outer edge of the grate and the outer wall of the combustion chamber, and accordingly 9. mechanieally-quite-flexible joint, such as is provided by the'fluent material I02 for example, is quite sufiiicient. Obviously limiting the weight-supporting connection to one side of the combustion air chamber (either to 5! or 52) and employing a flexible connection between the grate and its base on the other, minimizes the possibility of destruction of either part or rupture of the joint by reason of unequal expansions and contractions arising from the various parts being subjected to widely'difierent temperatures.

The grate i4 itself is designed with the view to minimizing the escape of coal and ash back through the perforations or air passages pierced in the grate wall (through which thecombustion air is led to the fuel on the grate), so that there may be no need for providing for the removal of coal and ash collecting within the air passage or chamber (within base l5) from which the air flows through these passages pierced inthe grate wall; or at most rendering a covered hand hole into this passage or chamber sufficient for the purpose. By the same means also, it will be observed from what follows, the air passages or perforations in the grate for the passage of combustion air to the fuel, may be kept substantially freed of ash'and fine fuel, the entry of ash and fuel intothe perforations being restrained and the indefinite accumulation of ash, and fuel therein being substantially prevented, so that these air, passages or perforations are kept generally well open for the flow of air therethrough. Primarily, to these ends, I so correlate the number of air passages provided in the grate 'wall, the sizes of the cross-sections of said passages, and the air pressure in the air chamber or passage from which the combustion air flows through the grate, that the velocity ofair within each air passage pierced in the grate Wallis adequate to blowin toward the mass of fuel substantially any piece or particle of coal crash that is small enough to enter the passage. At the same time, it will be understood, the air velocity isinsufficient to blow the mass of coal away from the grate, or to suspend the coal mass, or parts of it, inthe outwardly flowing air, the mass as a whole to the contrary resting on and being supported by the grate. It will be understood also that the air 'need'not be supplied in greater quantities per unit amount of coal burned than heretofore; as is well known, complete combustion of all the solid fuel supplied to a grate requires a quantity of air a few times greater than the quantity theoretically required to combine with all the carbon, theexact amount depending on the particular installation in each instance, and frequently for economic or. eiliciencyreasons less than the quantity required to cause complete combustion at the particular grate at hand is employed; in each instance I contemplate determining the quantity of air supplied through the grate on the same considerations as heretofore, so that the total quantity of air supplied in' any instanceis not greater than (and may be considerably less than) substantially the quantity needed to secure complete combustion of the fuel at the particular grate in hand. By reason of this correlation I both strongly tend to prevent the entry of pieces of ash and coal into the air passages and blow back again toward the mass of fuel and ash any pieces that may find theirway into the passages. To assist in obtaining this action, I. also employ, preferably, certain features of construction which are best shown in Figs. .3, 5, Sand 71 First, I make at least one dimension of the cross-section of each air passage or perforation in the grate relatively small, so that only the smallest of the mixed large and small pieces of ash and coal can enterthe'air passages. It will be observed that only one dimension of the cross-section of the passage need be small to accomplish this result, 1. e. the air passagescan have the form of long narrowslots as shown at I05 in Fig. 3, and I prefer this form. Usually (regardless of whether or not the passage is in the form of a long slot) I make the small dimension less than three-sixteenths of an inch, by preference less than one-eighth of an inch, and most preferably of the order of one-sixteenth of an inch; accordingly no particle the smallest dimension of which exceeds threesixteenths of an inch (or one-eighth of an inch, or one-sixteenth of an inch, as the case may be) can enter the passage, and the air velocity within the passage need be onlyvigorous enough to carry such small particles along with it. Conceivably this small dimension may be provided only at some point back from the fuel-bearing face of the grate or side or surface of the grate facing the fuel; that is to say, all dimensions-of the outlet openings of the passages at this side, face or surface of the grate may be greater than that indicated and the passages may be constricted to, say, one-sixteenth of an inch at the opposite surface of the grate, or it may be constricted to the chosen small dimension at some point inter mediate the two surfaces, but preferably (in order to prevent accumulation of larger particles within the passages) I make one dimension of the openings at the fuel-bearing surface of this small dimension regardless of what the shape and dimensions may be elsewhere. Most preferably therefore I give the air passages the form of long narrow slots at the side, face or surface of the grate facing the fuel, the slots being about onesixteenth of an inch wide, regardless of the shape and dimensions of the passages elsewhere. Also,

I preferably extend or locate these slots IE5 at this side of the grate at an angle of more than 40 from the vertical, as viewed from the vertical center line of the grate; more preferably, considerably more than 40 from the vertical; most preferably, I place them substantially horizontally (Fig. 3). The purpose of this placement of the long grooves or slots is to cause the fuel and ash to cross them more or less transversely, rather than slide lenthwise of them; if the particles are permitted to slide lengthwise of the slots they are more likely to be forced down into the slots. Second, by preference, (see Fig. 7) adjacent the fuel-bearing surface of the-.grate, I make the roofs i 06 of the grate perforations or air passages substantially horizontal or with a downward slope away from the surface of the grate facing the fuel, rather than with an upward slope from this surface, inasmuch as an upward slope, or rather (speaking in more general terms) a slope generally in the direction of the movement of fuel resting on the grate surface, tends to encourage the entry of particles and pieces into the air passage, while a slope against the direction of fuel movement (here a downward slope) tends to repel an entering particle. Likewise it is preferable that the floor I01 of each air passage be horizontal or slope upwardly, adjacent thesame surface of the grate, rather than slope downwardly, since in the latter case gravity will tend to carry back into the air chamber any dust that may find its way onto this floor. compromising between these two somewhat opposing requirements, I most preferably make both the floors and the roofs of the air passages substantially horizontal, at least adjacent'the side or surface'of the grate facing the fuel, as will be observed at ")6 and I0! in Fig. 7. Third, I propose to shield the outletends of the air passages from coal and ash passing over the grate adjacent the outlets, so as to fend'oif the traveling coal and ash from these openings. This can be done conveniently by terminating the air passages, i. e., forming their outlet openings, at the side or surface of the grate facing the fuel, in recesses I08 respectively re-entrant from the local general line of travel of the solid material passing over the grate;

in Fig. 7 the broken line I09 indicates generally the line 0? travel of the solid material over the grate shown in the drawings; it is the local" general line of travel for that part of the grate which is shown in that figure. These recesses I08 may be provided by protruding or fianging the surface of the grate; where the grate is built up of a number of superposed rings as in the presentinstance, recesses'are readily provided by making the internal diameter of each ring less than the internal diameter of the ring immediately above it, as appears clearly from Figs. 3 and 7. By fending off the solid material travelling over the grate, the tendency of the solid material to enter the air passages is correspondingly reduced; in the best cases, the solid material may pass straight across the opening from each air passage without striking either the top or bottom edge of it at all. Preferably also, to the same end, the part of the coal-bearing face of the grate immediately below each opening from an air passage is slanted more or less againstthe local general line of travel I09 of solid material over the grate, so as to further fend or direct the flow of solid material away from the opening to the air passage as it were; as an example, see the relation of the face marked IIO to the general line of travel I09 in Fig. 7. Fourth, I propose to so arrange the air passages or perforations that any pieces or particles entering them and not immediately blown out again, .are prevented from being either worked back into the air chamber by gravity or vibration of the grate, or thrust back by the subsequent entry of other pieces or particles; instead they are required to accumulate until the air flow in their neighborhood is again sufiicient to blow them back toward the surface or side of the grate facing the fuel. For example, a solid block of fuel at or near some part of the surface of the grate may so reduce the velocity of the air through the passage or passages in its neighborhood, for a time, that pieces or particles of fuel and ash entering such passages are not immediately blown out again. Therefore I propose to so arrange the air passages that any pieces or particles of ash or coal that may enter them, are forced to accumulate therein until the subsequent return of the local air velocity to normal, or the subsequent development of an abnormally high velocity, at that place, is able to blow them back toward the mass of fuel. In part this purpose is served by making each air passage horizontal for some distance away'from the surface of the grate facing the fuel as shown at I0'I in Fig. 7 and before described. In addition to this however I direct each air passage in an upward direction, at a point some distance away from the surface of the grate facing the fuel, or provide each air passage with an upwardly extending portion at such a point, as will be noticed near I20 in Fig. 7. In effect, this upwardly extending portion forms a dam preventing the free travel of solid particles or pieces backward toward the air chamber whence the air comes to the air passages. Obviously these five features thus described cooperate to prevent or restrain the backward escape of solid matter through the air passages, but (as will be observed from the claims which follow) my invention is not limited to the joint use of all these features. By such meahs however, I have found, the escape of fuel and ash back into the air chamber of forced underfeed stokers can be eliminated to such an extent that it is unnecessary ordinarily to provide any arrangement for cleaning out the air chamber.

The upward extensions of the air passages and the dam efiect mentioned above may be provided by the upwardly extending flanges IIS (compare Figs. 6 and 7) of the rings from which the grate here shown is composed. As a result of this flanged-ring construction, the air passages assume a Z-shape in vertical section (see Fig. 7). Also the flanges serve to center the rings with respect to each other, that is to say, prevent the rings being moved horizontally off each other. In general, each of the rings consists of a body portion III (see Fig. 6) having at its two edges a flange portion II5 extending down wardly and a flange portion H6 extending upwardly. To space these rings apart, one from another (to provide the air passages), intermediate members are interposed; conveniently these intermediate members can be provided by providing each ring with integral projections III, substantially only sufficient in number to carry the weight above them; these projections may have the form of radially extending flanges (see Fig. 5 also). The lowest of these rings rests on the grate-support. Preferably an internally cylindrical collar H8 is interposed between ihe lowest of these thin grate rings and the support (supporting wall 5|), this collar being long enough to assure, or to help assure, the uniform distribution of the upwardly rising coal throughout the grate. Above this lowest grate ring each grate ring rests on the ring immediately below it. In the present instance, the

radial flanges II'I extend downwardly not only I from beneath the flanges II5,;but also from beneath the outer parts of the body portions Ill of the rings and the superimposed weight may be carried in part at each of those points (see Fig. 7). As a matter of preference however, I desire that the air flows through the respective air passages shall be measured by some certain part of each air passage, by a constriction at some point as it were, and preferably that it be -measured by the spacing between the surfaces I06 and I01; preferably therefore I arrange to have the height of each passage at least no greater at this point than it is elsewhere, and I arrange to have the whole or-the major part of the weights carried by those parts of the projections I H which are immediately below the downward flanges II5, rather than by those parts of III which are attached to the ring bodies Ill. The result of this is that there is a minimum tendency for the proportioning of the total air flow between the. different air passages to vary as the rings expand and contract under the heat of the fire. Preferably however I do include a projection at, or extend the radial flanges III over, that part (of each ring) which is enclosed in the bracket H9 in Fig. 6, so as to prevent expansion or horizontal shifting of the rings, such as always occurs more or less, from bringing one (or more) of the downward flanges H5 into contact with the adjacent upward flange H6 and thereby shutting off air flow at that point. As a matter of fact, in order to prevent damage by unequal expansion and contraction of the various rings, I usually make the external diameter of each ring at the section marked by the bracket I I9, somewhat less (a small fraction of an inch less) than the internal diameter of the adjacent flange IIB outside it, as is apparent from the space at I20 in Fig. 7. 'It will be understood however that the minimum internal diameter of each ring. (at the coal-bearing face) is so much less than the maximum internal diameter of the body portion ill ofthe ring immediately below it, that the recesses I 08 are maintained at all times regardlessv of such. shifting of the rings, relatively toeach other, as the spacings at lliipermit.

If desired, the various rings of the grateycan be fastened together, for-example by boltssuch as I25 passing through lugsl26 and lflon u per and lower rings, (Fig; 3). Radial flanges ill on the lowermost of'the grate rings willv provide, if desired, for thexpassage for combustion air between this lowermost ring and thecylin-I drical member, H; also similar fianges" for;example can belprovided onthe bottom of this cylindrical member H8, or at thetop of the elbow walls ii, to provide for the admission of some air to the coal from underneath the cylindrical member. If desired, the grate structure can be tied down, for exampleby one or, two or'three bolts or links I28 fastened to some appropriate part ,(not shown) of the grate base i; generally however the weight of the .grate structure is quite suihcient to hold it in place and such tie bolts are not otprimary importance.

It will be obvious .ofcourse that various of the elements of grate construction discussed above are not limited in their application to grates of the kind illustrated;

I have also iound it 'desirable to employ a crusher, to crush or reduce to smaller dimensions ash or clinkerstoo 'largetoenter or be conveyed readily through the ash conduit], or whatever other means. oi ash disposal may be employed. Two members, one revolving in a path where it can pick up these large, pieces and the other standing (or even'moving) in the path of travel of the large pieces, will serve the purpose.-

Where, as in the machine-here illustrated, an ash paddle or scraper-P49 1; employed, this or these paddlesorifscrapers", ortheir supports,

can serve as the revolving member ormembers,

and it is only necessary to add another member, which may be stationary, near but outside the paddle path andhaving a surface which is nontangential or non-parallel to the paddle path at the point where the paddle passes this second member. Such'a second and stationary member is provided by the vertical plate ll '(Figs'. 2 and 8) here formed as a part of the fitting 21. It will be observed (Fig. 2) that the flat side of this plate facing the ash paddles is placed at such an angle that large ash,or clink'enj carried around by any one of the ash paddles, will be caught by and crushed against this-piate; This crusher arrangement forms nopart of theinvention-here claimed however. 7 t v t I It will be understood of course thatmy invention isnot limited to details of the embodiment of it above describedand referred to, nor" to the simultaneous embodiment of its various features,

except as appears hereinafter-in the claims. Iclaim; 1 1.,In asolid fuel stoker, the combination of a burner structure including a substantially annular underfeedcenterfeed grate, a base therefor provided with an inner'upwardly-rising wall forming a conduit for directing fuel toward the center opening throughsaid grateiand an outer upwardly-rising stationary wall reaching to said grate structure to provide a passageway for combustion air, said outer wall .beingprovided on its outer side with a substantially annularv substantially horizontaLbearingjcf a diameter materially' less than the diameter of said grate structure, and said outer wallalso being provided with a skirt extending downwardly over said bearing to shield the latter from ashes falling from said grate, a ring mounted on said bearing andfact that both said'encircling member andthe grate are out the bolt. 1

3. In a 'stoker for solid fuel, a grate, a base member therefor, an outwardly and upwardly flaring encircling member, the upper edge of which engages with the outer edge of, said grate and which cooperates with said base memberto provide a chamber through which the combustion air passes to the grate, and a boltiastening said grate and member together, said bolt being spaced inwardly from the point of engagement of contact with a mid portion of of said member and grate and passing-through said chamber. v r

4. In a stoker for solid fuel, a burner to be setin a furnace and which includes a substantiallytannulargrate perforated for the passage of combustion air and having a center opening for the reception of fuel, an. upwardly open conduitmember at said opening to direct solid fuel upwardly through said opening, an upwardly open-' ing substantially encircling member outside said 1 grate to provide a passage to direct combustion air to said grate, one of said members being out of grate-supporting relation to said grate, and

means providing a flexible Joint completing the enclosure of said passage by'said encircling memher.

5. In a stolrer for solid fuel, a burner to be set -in a furnace and which includes a substantially annulargrate perforated for the passage of combustion air and having a center opening forthe reception of fuel, means providingan upwardly opening conduit for the supply of fuel tosaid center opening of the grate, and encircling means," outside said grate, to provide a passage for combustion air to the perforations 01. said grate, one

of said-means carrying the weight-bf said grate Joint'to permit the grate and. said other means to expand and contract each substantially inde--;

pendently of the other, e tt 6. In a stoker for solid fuel, a burner to be set in a furnace and which includes a substantially annular grate perforated for the passage of combustion air and having. a center opening for the 7 reception of fuehan upwardly open conduit to supply fuel through said center opening and on which the grate rests and the weight of the grate 1 is I supported, and encircling means, outside said. grate, to provide a passage for combustion air to the perforations of said grate, said encircling means including a flexible joint to permit said grate and encircling means to expand and con-' tract each substantially independently of :the'

other.

-'7'. In a stokerfor solid fuel,a burner to beset in a iumace and which includes a substantially and the other of said means including a flexible! annular grate perforated for the passage of combustion air and having a center opening for the reception of fuel, an upwardly open conduit to supply fuel through said center opening and on which the grate rests and the weight of the grate is supported, and an encircling wall, outside said grate, to provide a passage for combustion air to the perforations of said grate, said encircling wall including an upwardly opening trough, a ring projecting downwardly from the outer periphery of the grate into the trough, and fluent material in the trough to seal the space between the ring and the trough.

8. The subject matter of claim '7, characterized by the fact that said fluent material is a solid material in granular form.

9. The subject matter of claim '7, characterized by the fact that said fluent material is sand.

10. In a stoker for solid fuel, the combination of a grate provided with a plurality of perforations for the passage of combustion air therethrough, means providing passageway means beneath said perforations, separate from the ash pit to which the ashes from the grate pass, for directing combustion air to said perforations, means for feeding fresh fuel to the grate from underneath the mass of fuel and ash resting on the grate and forcing the mass at the grate across the outlets of said perforations, and means for supplying combustion air to said passageway means under pressure, characterized by thefact that the number of the perforations, the sizes of the cross-sections of the perforations and the air pressure are so correlated that gas velocity through said perforations is sufficient to return to the fuel-bearing surface of the grate any pieces'of solid matter entering them but is insufficient to suspend in the air the masses of fuel opposite the perforations,

and air is supplied to the fuel on the grate in quantities not greater than substantially the quantities needed to secure complete combustion of the fuel.

i 11. In a stoker for solid fuel, the combination of a grate provided with a plurality of perforations for the passage of combustion air therethrough, said perforations being so shaped as to restrain the passage of dust and ash particles therethrough by gravity in the direction opposite 'to' the direction of the air flow, means providing passageway means beneath said perforations, separate from the ash pit to which the ashes from the grate pass, for directing combustion air to said perforations, means for feeding fresh fuel to the grate from underneath the mass of fuel and ash resting on the grate and forcing the mass at the grate across the outlets of said perforations, and means for supplying combustion air to said passageway means under pressure, characterized fuel-bearing surface of the grate the ash and dust by the fact that the-number of the perforations, the sizes of their cross-sections and the air pressure are so correlated that gas velocity through said perforations is sufficient to return to the particles entering the perforations, and air is supplied to the fuel on the grate in quantities not greater than substantially the quantities needed to secure complete combustion of the fuel.

12. The subject matter of claim 10, characterized by the fact that the fuel-bearing surface of the grate is provided with a recess or recesses, reentrant from the local general line of travel over the grate of the mass on the grate, into which the outlets from said perforations open.

13. The subject matter of claim 10, characterized by the fact that a dam is provided at each of at least some of said perforations to prevent the discharge, through said perforations, to the said passageway means, of ash and the smaller fuel pieces entering the said perforations until a quantity of ash and fuel pieces may have accumulated in said perforations.

14. The subject matter of claim 10, characterized by the fact that said perforations extend away from the fuel-bearing surface of the grate in a substantially horizontal direction, and a dam is provided at each of said perforations, exte- -riorly of the horizontally extending portions thereof, to restrain the discharge, to the said passageway means, of ash and the smaller fuel pieces entering the said perforations and accumulated in the said horizontal portions of the perforations.

15. The subject matter of claim 10, characterized by the fact that said perforations extend away from the fuel-bearing surface of the grate in a substantially horizontal direction, a dam is provided at each ofsaid perforations, exteriorly of the horizontally extendingportions thereof, to restrain the discharge, to the said passageway means, of ash and the smaller fuel pieces entering the said perforations and accumulated in the said horizontal portions of the perforations, and the fuel-bearing surface of the grate is provided with a recess or recesses, re-entrant from the local general line of travel over the grate of the mass on the grate, into which the outlets from said perforations open.

16. In a stoker for solid fuel, an upwardly and outwardly flaring grate having a plurality of perforations in the upwardly and outwardly flaring wall thereof for'the'passage of combustion air to the coal thereon, one dimension of a cross-section of each of said perforations being less than one-eighth of an inch, means to forcibly feed coal upwardly through said grate and across the outlets of said perforations, and means to supply combustion air to said perforations under such pressure that the gas velocity through said perforations is sufficient to return to the rising column of coal any pieces of solid matter that may enter the perforations, but at a velocity insuflicient to suspend in the air the masses of fuel opposite the perforations, the number of the perforations being such that air is supplied to the coal on the grate in quantities not greater than substantially the quantities needed to secure complete combustion of the coal.

1?. In a stoker for solid fuel, an upwardly and outwardly flaring grate provided with a plurality of perforations in an upwardly and outwardly flaring wall thereof for the passage of combustion air to coal thereon, the outlets from said perforations at the fuel-bearing face of the grate being return to the upwardly rising column of coal sub stantially any piece of solid matter entering them, but is insufficient to suspend in the air the masses of coal opposite the slots, the number of combustion-air perforations through the grate being such that air is supplied to the coal on the grate in quantities not greater than substantially the and the shorter dimensions of said slots are of the order of one-sixteenth of an inch.

19. In a stoker wherein fresh solid fuel is fed to the grate from underneath the mass of fuel and ash resting on the grate and the mass forced across the outlets of the combustion-air perforations in the grate, and the combustion-air is fed to those perforations by a passageway beneath the perforations and separate from the ash pit to which the ashes from the grate pass, a grate provided with a plurality ofperforations for the passage of combustion air therethrough and means for supplying combustion air under pressure to said passageway, the number and the sizes of the perforations and the air pressure of which are so regulated that the velocity ofthe gas through said perforations, is so related to the pieces of ash and fuel small enough to enter the perforations, that the flow of gas returns to the fuel-bearing surfaceof the grate any piece of solid matter entering the perforations, but is insufficient to suspend in the air the masses of fuel opposite the perforations, and air is supplied to the fuel on the grate in quantities not greater than substantially the quantities needed to secure complete combustion of the fuel.

20. An upwardly and outwardly flaring annular grate for solid fuel and means for feeding fuel upwardly through said grate, characterized by the fact that said grate includes a plurality of coaxial rings, each consisting of an annular body portion, an upwardly extending annular flange adjacent the outer edge of the body portion, and

a downwardly extending annular flange adjacent the inner edge of the body portion, said rings being arranged one above another and with the downwardly extending flange of each upper ring located within the upwardly extending flange of the ring next below it, and means interposed be- -tween substantially horizontal surfaces of the bodies and flanges of adjacent rings for spacing said rings apart to provide passages for the combustion air.

21. The subject matter of claim 20 characterized by the fact that the said spacing means includes projections extending from some of said annular flanges toward the respectively adjacent annular flanges of adjacent rings to provide the air passages with upwardly rising portions.

22, The subject matter of claim 20, characterized by the fact that the spacing means are radial flanges extending downwardly from each flange and body portion.

23. An upwardly and outwardly flaring annular grate for solid fuel and means for feeding fuel upwardly through said grate, characterized by the fact that said grate includes a plurality of superposed coaxial rings, each having a body portion, a downwardly extending flange adjacent its inner edge, and an upwardly extending flange adjacent its outer edge, the internal diameter of each of said rings being greater than the internal diameter of the adjacent ring respectively below it so that ledges are formed at the tops of the rings, and means spacing each of said rings from the ring below it so that passages through the grate are formed between each of said downwardly projecting flanges and the body portion of the adjacent ring below it.

GORDON M. PELTZ. 

